Blower door is 250 cfm less with Radon mitigation on vs off. Why????
Appreciate all the bright minds on here who have helped solve “mysteries” with my home. I have another problem hoping to get some ideas on. Blower door diagnostics were done both with and without my radon fan/system running. Radon fan is on home exterior with pipes running underneath 12 mil vapor barrier in conditioned and sealed crawl). We had previously experience significant humidity in crawl space while radon fan was operating. Now ( thanks to the help of everyone on here) we have corrected that problem and the crawl space now stays pretty constant.
My question is: Why are the blower door results 250 cfm lower when the radon mitigation system is on( sub slab/Fan tech HP 220) on, than when it’s off? Blower door test was 3428 cfm with Radon on, 3678 with Radon mitigation off.